Device for multiplexing video signals

Abstract

This invention relates to a system that permits a video tape recorder to simultaneously record a plurality of independently occurring events. The system causes the events to be multiplexed before they are recorded and a coded signal to be recorded on the tape so that when the tape is played back, the events may be demultiplexed in the same order that they were recorded.

What is claimed is: 
     
       1. A system that permits a video tape recorder to simultaneously record a plurality of independently occurring scenes involving slow image movement that are produced from stroke writing systems, said system comprising: a. a plurality of first scan converting devices that convert and store the information from a stroke writing display system in a separate said scan converting device in order to allow sufficient time for the data to be written into one of said scan converting devices;   b. a plurality of first switching devices that are coupled to a specified video signal output of said first scan converting devices to provide a signal comprised of only pairs of even frames;   c. a plurality of second scan converting devices receiving information from a stroke writing system for the purpose of converting and storing the information contained in each scene in a separate said second scan converting device;   d. a plurality of second switching devices that are coupled to a specified video signal output of said second scan converting devices to provide a signal composed of only pairs of odd frames;   e. a plurality of first mixing devices that are coupled to the output of said first switching devices;   f. a plurality of second mixing devices coupled to the output of said second switching devices;   g. timing means coupled to said first and second scan converting devices, and first and second mixing devices, and said first and second switching devices for causing information to be stored and erased from said first and second scan converting devices at certain specified times and for causing information to be read from said first and second switching devices at certain specified times wherein said timing means comprises:   a sync generator whose output signals are constant timing pulses that are coupled to the input of said first and second scan converting devices to insure that the output of one of said first plurality of switching devices consists of alternate even frames and the output of the other one of said first plurality of switching devices consists of the other alternate even frames, and to insure that the output of one of said second plurality of switching devices consists of odd frames and the output of the other one of said second plurality of switching devices consists of the other alternate odd frames;   a plurality of cascaded flip-flops whose inputs are coupled to the output of said sync generator;   a plurality of dividers whose inputs are coupled to said cascaded flip-flops so that the frequency of said timing pulse may be changed; and   a plurality of first gates and inverters whose inputs are coupled to said sync generator, said cascaded flip-flops and said dividers and whose outputs are coupled to said first and second scan converting devices and said first and second switching devices;   h. code generating means for causing a code to be written on the video tape that is being recorded on said video recorder, whereby information that was stored in said first and second scan converting devices will be multiplexed on an odd even frame basis and mixed with said coded signal so that a plurality of independently occurring scenes may be synchronously recorded at the same time.   
     
     
       2. The system according to claim 1, further including means coupled to the output of said first and second switching devices and the output of said first and second signal mixing devices for monitoring at various stages the scenes processed by said system. 
     
     
       3. The system according to claim 2 wherein said means for monitoring comprises: a. a third switching device coupled to the output of said first switching device and the output of said first signal mixing device; and   b. a display monitor coupled to said third switching device so that an observer may view at various stages the scenes processed by said system.   
     
     
       4. The system according to claim 3 wherein said third switching device is a manually controllable selector. 
     
     
       5. The system according to claim 1 wherein said first plurality of first and second scan converting devices are a plurality of stroke writers to raster scan converters. 
     
     
       6. The system according to claim 1 wherein said first and second switching devices are a plurality of analog switches. 
     
     
       7. The system according to claim 1 wherein said code generating means comprises: a. a timer coupled to the output of said timing means;   b. a pulse generator coupled to the output of said timer;   c. a second gate whose inputs are coupled to the output of said pulse generator and said timing means; and   d. a third mixing device whose inputs are coupled to the output of said second gate and the output of said first and second mixing devices.